[unreadable] This proposal will provide new training and a significant shift in career direction for the P.I. from fields of fundamental physical and organic chemistry to applied biomedical imaging and spectroscopy. Studies will be performed at the OSU Biomedical Spectroscopy and Imaging Center, a unique training environment with emerging state-of-the art techniques and with additional learning opportunities in experimental physiology and cell biology that will ensure progress toward independence of the P.I. The overall experimental plan will develop new biomedical imaging and spectroscopy applications for a group of pH- and thiol (SH)-sensitive nitroxides, previously synthesized by the P.I. and colleagues. Current methods for spatial and temporal detection of pH and SH in living tissues and organisms either have significant limitations or do not exist. Therefore, these new approaches could represent a breakthrough in physiologic monitoring in a variety of settings. Experiments will focus on applications related to cardiac ischemia and ischemia-reperfusion injury. The specific aims are: (SA1) To critically evaluate existing and newly synthesized pH- and SH-sensitive nitroxides as functional probes for in vivo electron paramagnetic resonance (EPR) applications. Functional sensitivity, stability towards reduction in biological tissues and capacity for in vivo/cellular distribution will be studied. A series of new probes will also be tested which are specifically designed to enhance these probe attributes. (SA2) To develop functional EPR-based spectroscopy and imaging for the investigation of time and spatially-resolved pH and SH content in living tissues. Initial studies will optimize techniques for probe administration, maximization of spatial and intensity resolution and minimization of toxicity. The experiments are planned using these techniques to evaluate a new hypothesis: namely, that pH-induced changes in myocardial buffering capacity, developed during preconditioning, are important in functional protection of the heart during subsequent prolonged ischemia. Preliminary experiments demonstrate the potential importance of this relatively unknown mechanism. (SA3) To obtain the necessary tools and skills in imaging and in medical science to bridge the interface between physical chemistry, applied biomedical sciences and imaging technology. The success of this project may have a significant impact on the future of bioimaging applications to medicine. [unreadable] [unreadable]